A gas generator of the same type as the present is known for example, from DE 39 14 690 A1.
The known tubular gas generator has a cylindrical outer tube which constitutes the housing of the gas generator and open end faces of the housing are closed by cover elements. Arranged coaxially in the outer tube is a cylindrical inner tube of smaller diameter; this inner tube defines a combustion chamber in which is housed a gas-generating material ignitable by means of an igniter unit. The inner tube is provided with several outflow openings in a tube wall. In the annular space between the inner tube and the outer tube are filter elements which generally consist of a number of layers of wire mesh, steel wool and/or non-woven metal filament fabric. The combustion gas issuing from the outflow openings of the inner tube flows through the filter elements which trap the solid and liquid or condensed combustion products, and passes out, cleaned, via gas exit openings in the outer tube.
In order to maintain opening gas pressures for the airbag which are constant at all temperatures, it is known to close the outflow openings on the inside of the inner tube by means of narrow metal strips welded or glued in place.
A disadvantage of the use of such strips to provide damming is that with the known gas generators, it is virtually impossible to automate a welding or gluing procedure with an acceptable cost, so that the aforementioned method is much too complicated and thus is too expensive. Also, such narrow strips may not provide adequate damming.
It is also known to close the outflow openings on the outside of the inner tube by means of a narrow sealing strip, of uniform width. The strip is bonded to the inner tube by an adhesive. This is intended to prevent moisture from getting into the interior of the inner tube and into the gas-generating material. The sealing strip in this case is longer than the periphery of the inner tube so that there is an overlap.
Sealing against moisture, as heretofore described, has not proved adequate. It has been found that during a required storage time of 10 years, moisture is still able to penetrate and causes the gas-generating material to become unusable.